Mitigation of Dead Zones

The key to reducing the size and number of low-oxygen dead
zones in coastal waters is to reduce the input of nutrients into estuaries and
the coastal ocean. Nutrient-reduction
strategies are a key part of efforts to restore the health of
Chesapeake Bay.

Researchers at the Virginia Institute of Marine Science
(VIMS) collaborate with colleagues around the world to address the problem of
marine dead zones, including efforts to

TMDLs

An important strategy in reducing the size and duration of
dead zones is establishment of a total daily maximum load (TMDL) for the nutrients
(nitrogen and phosphorus) that encourage dead-zone formation. TMDLs are similar
to the "recommended daily allowances" found on food labels, and
indicate the maximum amount of a pollutant that can enter a water body without
causing a water-quality indicator such as dissolved-oxygen levels to cross a
defined threshold.

Water-quality thresholds can vary depending on a water
body's "designated use." These include use by native marine life, commercial
harvesting of fish and shellfish, and recreational uses such as swimming and
boating. The thresholds also recognize seasonal variations in nutrient inputs
and dissolved-oxygen levels, as well as difference in dissolved-oxygen levels
in different Bay habitats.

VIMS researchers work with colleagues in state and federal
agencies on all 3 steps of the TMDL plan for nutrient pollution that was
set forth in the Chesapeake 2000 Agreement:

Develop the TMDLs needed to meet water-quality standards.

Develop a TMDL implementation plan.

Implement the TMDL plan, and monitor water quality
to determine if water-quality standards are being attained.

Read More

Read more about VIMS' role in the TMDL program for nutrient
pollution in Chesapeake Bay: